I recently brewed a partial mash version of the sweet stout in Brewing Classic Styles. I mashed the following:
1 lb American 2-row
1.5 lb Maris Otter
1 lb Black Patent (yes, that's what the recipe calls for)
0.75 lb Crystal 80
0.5 lb Pale Chocolate
I added 13 ounces of lactose to the resulting wort to get 3 gallons of wort with a pre-boil gravity of 1.053 (2 points higher than what the recipe calls for.
I then added 5.8 pounds of light LME at knockout, and after topping off, I was left with 5.25 gallons of wort with a specific gravity of 1.063. That's 3 points higher than the recipe. I used S-04.
My question is this: the recipe calls for 1 pound of lactose, but my LHBS only had 13 ounces. Should I add three ounces and add it at bottling? I checked the gravity yesterday (after 12 days in primary), and it's right around 1.025. I don't expect it to drop any lower, but I will check again before I bottle. The sample tasted great. My thinking is that since I got a greater efficiency with my mash and added a little bit more LME (half a pound) than the recipe called for, than I will have more residual sugars anyway and that 3 ounces of lactose isn't a big deal.
Am I right in my reasoning?